Ferroelectric capacitors have various uses in RF systems including as voltage-tunable devices. Some benefits of ferroelectric capacitors are small size, integration of different values and functions of capacitance, and low cost. Applications for ferroelectric capacitors may include tunable filters, voltage controlled oscillators, tunable phase shifters, tunable matching networks, low-impedance power supplies, decoupling high-frequency signals at an IC bonding pad, or others.
Integrated circuits including ferroelectric capacitors may, for example, be used in portable electronics for low-power wireless communication (e.g., cellular phones, pagers, PDAs, and so forth), directional antenna systems, high clock-rate microphones, miniature DC to DC converters, or other devices.
The fabrication of tunable ferroelectric capacitors can sometimes lead to undesired conditions. For example, a hillock that forms on a bottom electrode can cause defects and deformations resulting in a reduction in breakdown voltage of the dielectric film. As another example, vertical dendrite growth can cause capacitor failure in the field during use.
Current techniques of depositing high-K tunable dielectric materials can have limited throughput and thus high capital and manufacturing costs. Current techniques can also have limitations in flexibility of composition that may not allow the best optimization or improvement of RF and DC properties of the dielectric stack.